For gotox, CFG construction models the indirect-jump target set in
insn_aux_data->jt, but do_check() later follows targets from the runtime
PTR_TO_INSN register's own INSN_ARRAY map. If the same gotox can be
reached with PTR_TO_INSN values from different maps, do_check() can accept
a target outside the subprog that CFG allowed for the gotox instruction.
On x86, that can transfer control into another subprog without a matching
BPF call frame and crash when the program is run.
Fix this by rejecting gotox map targets outside the current gotox subprog.
Add a regression test covering the two-map cross-subprog case.
Validation:
unpatched bpf-next 7bfb93e3475b with the new selftest:
bpf_gotox/check-cross-subprog-gotox-target: FAIL
cross_subprog_gotox_prog_load: actual 23 != expected -22
__TEST_PROGS_RC__=1
patched bpf-next 7bfb93e3475b + this series:
bpf_gotox/check-cross-subprog-gotox-target: OK
./test_progs -t bpf_gotox/check-cross-subprog-gotox-target
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
__TEST_PROGS_RC__=0
v1 -> v2:
- Validate gotox runtime targets against the current subprog bounds instead
of scanning the CFG jump table.
- Fix the selftest expected error from -EACCES to -EINVAL.
v1:
https://lore.kernel.org/bpf/20260609-f01-02-gotox-bpf-next-v1-0-b441d63a1...@mails.tsinghua.edu.cn/
Signed-off-by: Nuoqi Gui <[email protected]>
---
Nuoqi Gui (2):
bpf: Enforce gotox targets against subprog bounds
selftests/bpf: Add cross-subprog gotox target coverage
kernel/bpf/verifier.c | 21 +++++++
tools/testing/selftests/bpf/prog_tests/bpf_gotox.c | 73 ++++++++++++++++++++++
2 files changed, 94 insertions(+)
---
base-commit: 7bfb93e3475be9de894f1cecd3a727d3e1649b03
change-id: 20260613-f01-02-gotox-bpf-next-v2-send-8c48c9357dde
Best regards,
--
Nuoqi Gui <[email protected]>
